Through the full support of Cobain’s widow, Courtney Love, Cobain’s family, and bandmates, director Brett Morgen (“The Kid Stays in the Picture“) spent seven years engrossed in cassette tapes, videos, and Cobain’s journals to make the first authorised film on the face of ’90s grudge rock.

The portion of “Montage of Heck” that explores the relationship between Cobain and Love is predominately of recordings Love’s ex-boyfriend would shoot when he was over their house and home videos Cobain and Love shot themselves. And there’s a half-minute or so of Cobain and Love in bed together. There’s nothing graphic, but Love was shocked Morgen found it.

“Me and Kurt only had this one tape,” she said, “so we recorded over and over [on the same tape]. Everyone makes one sex tape once in their lives and we did.”

With an embarrassed look, Love added of Morgen, “I thought he’d never catch this and he caught it.”

“Kurt Cobain: Montage of Heck” is currently playing at the Tribeca Film Festival and will air on HBO May 4.